The present invention relates to a laser light emitting device using a multi-mode fiber and a laser surveying instrument comprising the laser light emitting device.
A pump light, emitted by a laser diode is entered into a cavity via a multi-mode fiber, and at the cavity, pumping is performed on the pump light. The pump light is resonated, amplified and outputted as a laser beam.
The multi-mode fiber to guide the pump light to the cavity is subject to a deformation as required such as bending, twisting, etc. in the process of installing on a device or an instrument. Stress is generated inside the multi-mode fiber due to deformation and the generated stress exerts influence on an advancing condition of a laser beam which propagates the multi-mode fiber, causes non-uniformity of light intensity distribution and deteriorates a quality of the laser beam.
For instance, in a case were a laser light emitting device is used in a laser surveying instrument, non-uniformity of the light intensity distribution exerts influence on an accuracy of distance measurement because non-uniformity of the light intensity distribution gives influence on a photodetection intensity of a reflection light.
For this reason, it is necessary to uniform the light intensity distribution of the pump light entering the cavity.
Conventionally, the laser diode is selected or a light emitting condition of the laser diode is adjusted or the like so that light intensity distribution of the pump light emitted from the multi-mode fiber would be uniform under a condition where the multi-mode fiber is fitted on the laser diode.
For this reason, an yield of the laser light emitting device is low, much cost for adjustment is needed, etc. and the laser light emitting device is of high cost.